A power semiconductor device requires a low turn-on resistance or a low saturation voltage to reduce the power loss in a conduction state while providing a flow of very large current. Further, the powder semiconductor device basically requires a characteristic in which the powder semiconductor device withstands a reverse high voltage of the P-N junction which is applied to both ends of the power semiconductor device in a turn-off state or at the moment when a switch is turned-off, that is, a high breakdown voltage characteristic.
Out of powder semiconductor devices, a metal oxide semiconductor field effect transistor (MOSFET) is the most general field effect transistor in digital circuits and analog circuits.
MOSFET may be classified into planar gate MOSFET and trench gate MOSFET according to the type of the channel. The planar gate MOSFET has a long current path since the channel region is positioned in parallel with a semiconductor surface, and has a relatively high turn-on resistance due to the presence of a junction field effect transistor (JFET) region. The trench gate MOSFET does not have a JFET region, but can reduce the breakdown voltage due to the electric field concentrating on the bottom end of the trench.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.